Thermal Efficiency Apparatus - TD-8564

Overview

The Thermal Efficiency Apparatus is a real heat engine that can be used to investigate and clarify the principles at work in Carnot's ideal heat engine. Like Carnot's model, it can be operated as a heat engine, converting heat into work, or operated in reverse as a heat pump, transferring heat from a cold source to a hot source. Results are typically accurate to better than 5%.

Typical Experiments:

Real Efficiency vs. Temperature Difference

Carnot Efficiency

Heat Pump Coefficient of Performance

Thermal Conductivity

Load of Optimum Performance

How It Works

The key element is a Peltier device, a semiconductor that turns thermal energy
into electrical energy. The device is sandwiched between two blocks of aluminum
which act as the hot and cold reservoirs. One block is water-cooled using the
built-in pump. The other is electrically heated. A thermistor is implanted in
each block so temperatures can be measured with a digital ohmmeter.

The
energy supplied to this heat engine is the electrical energy used to heat the
aluminum block. The heat engine does work by running a current through the load
resistor. Both the energy in and the work out are easily determined by measuring
currents and voltages.

Then it's simple to calculate the real efficiency
of the engine (power out/power in) as a function of the operating temperatures.
By investigating other modes of operation, energy losses can be measured.
Students can use these results to determine the Carnot efficiency and to compare
it with the theoretical value for each set of operating temperatures.